Friday 20 July 2012 08.47 EDT
First published on Friday 20 July 2012 08.47 EDT

Twelve people are dead and up to 50 injured in a Denver suburb after a masked gunman opened fire at a late-night screening of the new Batman film, The Dark Knight Rises.

Witnesses speaking to the local KOA radio station said the gunman was wearing a gas mask and had released a smoke or teargas bomb before the shooting started. One witness described to CNN a "guy slowly making his way up the stairs and firing, picking random people".

Police have taken a suspect into custody. A man said to be in his early 20s carrying a knife, rifle and handgun and wearing a bulletproof vest was arrested without a struggle in a car park behind the cinema.

The police chief in the Denver suburb of Aurora, where the shooting took place, said there was no evidence of a second gunman.

"This is a horrific event," Dan Oates told reporters. He said police had checked for explosives in the cinema and car park and secured both areas.

"Our hearts go out to all of the family. We have mobilised the witnesses that we could get our hands on to an area high school where de-briefings are under way," he said.

Local hospitals were alerted to a "mass casualty incident". Media reports said 10 people died at the scene and four died later in hospital.

A witness told CNN: "We heard anywhere from 10 to 20 shots and little explosions going on. Shortly after that we heard people screaming. Then they came on PA system and said everyone needed to get out. As soon as we got out, there were people running around and screaming."

Other witnesses said the gunman opened fire during a shootout scene in the movie, leading to confusion.

Police said the first emergency call was made at 00.39am local time.

A spokeswoman for Denver's Swedish Medical Center said three people had been admitted to the hospital with gunshot wounds and were in a critical condition.

Another hospital, Denver Health, had received six wounded, one of whom was in critical condition, a spokeswoman said.